Rhombus-shaped Co3O4 nanorod arrays for high-performance gas sensor

Rhombic Co3O4 nanorod (NR) array-based gas sensor was successfully fabricated via a facile two-step synthesis approach, including the formation of rhombic Co(OH)F NR arrays as precursor followed by thermal conversion to porous Co3O4 without altering the original shape. Good ohmic contacts with the electrodes and intensive contact with the substrates avoided complicated fabrication process of gas sensors. The NR arrays annealed at 450 °C showed high-performance of ethanol detection. The response to 500 ppm ethanol gas reached ∼71 and the optimal working temperature was as low as 160 °C. Meanwhile, the sensor exhibited good response/recovery kinetics (90 s and 60 s), outstanding selectivity over several interferential gases and good stability tested in 3 months. In addition, the sensor could detect ethanol at a low detection limit (<10 ppm), which exhibited good reproducibility. The high ethanol gas sensing performance of the Co3O4 NRs can be explained by a typical p-type behavior with the one-dimension structure, nano-porosity, large specific surface area, good crystallinity and the open space of nanorod arrays.